THE PRECIPITINS AND THEIR ANTIBODIES 279 



which is evidently impossible,/ is infinite. Then/ passes 

 through the value 12 between n = 0.6 to 0.7, and sinks 

 to 5.3 between n 0.8 and n 0.9. 



In a very excellent memoir Fuld and Spiro 1 have made 

 it probable that the " antirennet " contained in the normal 

 serum of horse blood is a so-called pseudo-globulin 2 which 

 acts in such a manner that it binds a part of the calcium 

 ions and thereby hinders, or better retards, the coagulation. 

 As we have seen before (cf. p. 74), the influence of the 

 quantity of free calcium ions upon the time of coagulation 

 is as large as that of the quantity of rennet. Therefore 

 a binding of the calcium ions in a certain proportion has 

 the same effect as a neutralisation of rennet in the same 

 proportion. In this case the quantity of calcium salt of 

 the para-casein regulates the velocity of coagulation. The 

 salts of calcium with para-casein and with the pseudo- 

 globulin must be dissociated to a very low degree, and 

 for the sake of simplicity we may suppose that the degree 

 of dissociation of the two salts and of the acids in the pres- 

 ence of a given quantity of calcium ions is such that we 

 may make use of the formula of Guldberg and Waage. 

 This may at least be regarded as a preliminary approxima- 

 tion, which we may employ until the properties of the 

 reacting compounds have been better examined. Then if 

 the quantity of para-caseate of calcium in the absence of 



1 Fuld and Spiro: Zeitschr. f. ph. Ch., 31. 147 (1900). 



2 On precipitation with ammonium sulphate, euglobulin and pseudo-globu- 

 lin separate out. Their aqueous solution is dialysed, then the euglobulin 

 precipitates and the pseudo-globulin remains in solution. The euglobulin has 

 a coagulating influence on casein. The pseudo-globulin retards the coagu- 

 lation, even if caused by papayotin, cynarase or euglobulin, as well as by 

 rennet. 



